System for assisting the regeneration of depollution means included in a motor vehicle exhaust line

Abstract

In a system for assisting the regeneration of depollution apparatus associated with an oxidation catalyst implementing an OSC function, constituting a supply of oxygen and integrated in an exhaust line of a motor vehicle diesel engine, in which the engine is associated with a common rail for feeding its cylinders with fuel, the running conditions of the vehicle are analyzed and compared with predetermined threshold values, to control the engine in a first regeneration mode of operation with a lean mixture when running conditions are above the threshold values, or in a second regeneration operating mode implementing sequences in which engine operation alternates between stages of rich mixture operation and of lean mixture operation when conditions are below the threshold values.

1. A method of assisting the regeneration of a depollution device by O 2  combustion of soot,
 wherein the depollution device is associated with an oxidation catalyst implementing an OSC function, constituting a supply of O 2  and integrated in an exhaust line of a motor vehicle diesel engine, in which the oxidation catalyst constituting a supply of O 2  is located upstream of the depollution device and the engine is associated with a common rail for feeding its cylinders with fuel, 
 the method comprising:
 analyzing the running conditions of the vehicle, and 
 comparing them with predetermined threshold values including a threshold value of a temperature level in the vehicle exhaust line, and 
 controlling the engine
 in a first regeneration operation mode by molecular O 2  combustion of the soot with a lean mixture when running conditions are above the threshold values, or 
 in a second regeneration operating mode by molecular O 2  combustion of the soot implementing sequences in which engine operation alternates between stages of rich mixture operation and of lean mixture operation as long as conditions are below the threshold values including the temperature threshold value, to raise the temperature level in the vehicle exhaust line as long as the temperature is under the temperature threshold value, 
 
 
 so that during rich mode, oxygen is released from the oxidation catalyst to promote combustion of reducing agents, so as to raise temperature levels at an inlet to the depollution device. 
 
     
     
       2. A method according to  claim 1 , wherein the depollution device comprises a NOx trap. 
     
     
       3. A method according to  claim 1 , wherein the fuel includes an additive that is to be deposited together with the particles with which it is mixed on the depollution device in order to facilitate regeneration thereof. 
     
     
       4. A method according to  claim 1 , wherein the depollution device is impregnated with an SCR formulation, performing a function of oxidizing CO/HC. 
     
     
       5. A method according to  claim 1 , wherein the running conditions are determined from:
 the load on the engine; 
 its running speed; and 
 the speed of the vehicle. 
 
     
     
       6. A method according to  claim 1 , wherein the oxidation catalyst-forming means implementing an OSC function constituting a supply of O 2  stores oxygen in the form of at least one of ceria CeO 2  and a composite oxide of cerium and zirconium. 
     
     
       7. A method according to  claim 1 , wherein, in the second regeneration operating mode the alternating stages of rich mixture operation and of lean mixture operation include at least a first stage of rich mixture operation, followed by a second stage of lean mixture operation, followed by a third stage of rich mixture operation, wherein the rich mixture operation stages have approximately a same duration. 
     
     
       8. A method according to  claim 1 , wherein an outlet of the oxidation catalyst-forming means feeds into an inlet of the depollution device in the exhaust line. 
     
     
       9. A method according to  claim 1 , wherein the depollution device comprises a particle filter. 
     
     
       10. A method according to  claim 9 , wherein the particle filter includes a catalyst. 
     
     
       11. A system for assisting the regeneration of depollution means by O 2  combustion of soot,
 wherein the depollution means is associated with oxidation catalyst-forming means implementing an OSC function, constituting a supply of O 2  and integrated in an exhaust line of a motor vehicle diesel engine, in which the oxidation catalyst-forming means constituting a supply of O 2  is located upstream of the depollution means and the engine is associated with common rail means for feeding its cylinders with fuel, 
 the system comprising means for analyzing the running conditions of the vehicle, for comparing them with predetermined threshold values including a threshold value of a temperature level in the vehicle exhaust line, and for controlling the engine (i) in a first regeneration operating mode by molecular O 2  combustion of the soot with a lean mixture when running conditions are above the threshold values, and (ii) in a second regeneration operating mode by molecular O 2  combustion of the soot implementing sequences in which engine operation alternates between stages of rich mixture operation and of lean mixture operation as long as conditions are below the threshold values including the temperature threshold value, to raise the temperature level in the vehicle exhaust line as long as the temperature is under the temperature threshold value, 
 so that during rich mode, oxygen is released from the oxidation catalyst-forming means to promote combustion of reducing agents, so as to raise temperature levels at an inlet to the depollution means. 
 
     
     
       12. A system according to  claim 11 , wherein the depollution means comprise a NOx trap. 
     
     
       13. A system according to  claim 11 , wherein the fuel includes an additive that is to be deposited together with the particles with which it is mixed on the depollution means in order to facilitate regeneration thereof. 
     
     
       14. A system according to  claim 11 , wherein the depollution means are impregnated with an SCR formulation, performing a function of oxidizing CO/HC. 
     
     
       15. A system according to  claim 11 , wherein the running conditions are determined from at least one of:
 the load on the engine; 
 its running speed; and 
 the speed of the vehicle. 
 
     
     
       16. A system according to  claim 11 , wherein the oxidation catalyst-forming means implementing an OSC function constituting a supply of O 2  stores oxygen in the form of at least one of ceria CeO 2  and a composite oxide of cerium and zirconium. 
     
     
       17. A system according to  claim 11 , wherein, in the second regeneration operating mode, the alternating stages of rich mixture operation and of lean mixture operation include at least a first stage of rich mixture operation, followed by a second stage of lean mixture operation, followed by a third stage of rich mixture operation, wherein the rich mixture operation stages have approximately a same duration. 
     
     
       18. A system according to  claim 11 , wherein an outlet of the oxidation catalyst-forming means feeds into an inlet of the depollution device in the exhaust line. 
     
     
       19. A system according to  claim 11 , wherein the depollution means comprise a particle filter. 
     
     
       20. A system according to  claim 19 , wherein the particle filter includes a catalyst.